1. Field of the Invention
This invention pertains generally to the field of aviation and the construction of flight paths used by avionics equipment installed in an aircraft.
2. Description of the Related Art
A Flight Management System (“FMS”) for both commercial and military aircraft usually contains an active flight plan that can be used to guide the aircraft from one location to another and to compute critical flight parameters such as BINGO (i.e., remaining flight time before returning to base without using reserve fuel). The active flight plan is usually created by an off-line route planning program or pilots and is loaded into FMSs before takeoffs. However, due to unforeseen events such as weather hazards and pop-up threats, the active flight plan may need to be modified in-flight to guide aircraft away from pop-up hazards. Most of current FMSs have the auto routing capability to automatically re-plan a new flight plan in-flight upon pilot request. However, the auto routing functions in FMSs usually re-plan a new path based only on pre-stored navigation waypoints without any consideration of terrain and pop-up hazards. The primary purpose of this auto routing function is to increase the autonomy of the flight deck.
To enhance the survivability of Unmanned Aerial Vehicles (“UAVs”), new auto routing requirements are coming from military users to enhance the current auto routing function in FMS or Mission Computer System (“MCS”). Current UAVs or manned aircraft controlling them are equipped with multiple tactical data links to receive threat information from various sources in-flight. A data correlation function is used to fuse this threat information and produce a clear and concise picture about the threat environment surrounding the aircraft. With this concise threat picture and a detailed 3D terrain database, this new real-time auto router can automatically generate a safe and flyable 3D flight plan and present it to pilots controlling UAVs for approval well ahead of pop-up threats being encountered. The approved flight plan can then be data linked to MCS in the UAV. Therefore, a real-time auto router increases the survivability of the unmanned aircraft.
Technical challenges imposed by these new real-time auto routing requirements include the following: search data in a terrain database over a large area such as a circle with a radius of one-hundred fifty (150) nautical miles (“nm”) because the re-planned path can be more than 150 nm long; avoid multiple 3D threats simultaneously; re-plan a 3D path that is flyable; complete the re-planning task within seconds; and host the software in an onboard embedded platform with a constrained computational speed. In other words, the technical challenges are primarily due to the fact that a huge amount of data needs to be processed within seconds and in an embedded platform with a constrained computational speed.
Route planning has been an active research area over the past forty (40) years, especially in the robotic community; however, in the robotic community, most of real-time route planning algorithms were developed to construct a safe path with a range up to a couple of hundreds of meters—not 150 nautical miles. In UAV community, some route planning algorithms were developed to be coupled with a flight control system to serve as an integrated real-time motion planner that generates outer-loop control commands at high rates. The re-planning distance is usually limited to be within a couple of kilometers. Therefore, there is a clear need to develop an innovative real-time auto router that can meet the emerging military as well as civilian requirements.